Method for winding a heating wire

ABSTRACT

An apparatus for winding a heating wire on a core for forming the inner periphery of an electric melt-bonding joint which comprises a core in a generally cylindrical shape which is capable of rotating around its axial center, the core being relatively moved in the axial direction with respect to a heating wire, an engaging piece mounted on the core, which has a holding portion for holding a heating wire, and a fixing means to fix a terminal pin to the leading end of the heating wire, wherein the engaging piece has a holding portion for holding the terminal pin, whereby the heating wire is wound on an outer peripheral portion of the core by rotating the core.

The present invention relates to a method of and an apparatus forwinding a heating wire on an outer peripheral portion of a core forforming by injection molding an electrically melt-bonding joint in whichthe heating wire is embedded in the joint.

In recent years, when synthetic resin pipes such as gas pipes, waterpipes or the like are connected to each other, an electricallymelt-bonding joint A in which a heating wire 1 is embedded in the innerperipheral surface of its socket portions as shown in FIG. 8 have beenused. When the pipes are connected with the electrically melt-bondingjoint A, the synthetic resin pipes are inserted to the socket portionsat both ends and a power source is connected to terminal pins 1aattached to the heating wire 1 to heat the wire whereby the syntheticpipe is melt-bonded to the joint.

A method of making the electrically melt-bonding joint, which has beenwidely used, comprises a winding step wherein the heating wire is woundin a coil form by a predetermined number of turns on an outer peripheralportion of a core for forming the inner periphery of the joint, aterminal processing step wherein the heating wire is cut to have apredetermined length, and each end portion of the heating wire isinserted into each terminal pin to thereby electrically connect theterminal pins to the heating wire, and a shaping step wherein the coreon which the heating wire is wound in a coil form is set in a metalmold, and molten resin is injected into the metal mold.

However, the conventional method had problems in the winding step andthe terminal processing step in the manufacture of the electricallymelt-bonding joint. Namely, when the terminal pins are electricallyconnected to both ends of the heating wire after the heating wire hasbeen wound on an outer peripheral portion of the core, it was necessaryto conduct operations for connecting the terminal pins to the heatingwire in a limited narrow space near the core. Accordingly, it wasdifficult to employ automation or a linear arrangement for the windingstep and the terminal processing step, and these steps were obliged torely on manual labor. Further, in a case that after the heating wire hasbeen wound on an outer peripheral portion at an end of the core, thewire has to be wound on an outer peripheral portion at the other side.In this case, the distance of wound portions is spaced as indicated bybroken lines in FIG. 8. Thus, when the spacing operation and the windingoperation for the heating wire are conducted manually, deflection of theposition is apt to occur, and a correcting operation by manual labor isneeded after the winding operation.

Accordingly, in the conventional method, there was scattering in thequality of products and reduction in yield or production cycle, wherebyit was difficult to supply the products at a lower price.

It is an object of the present invention to provide a method of and anapparatus for winding a heating wire capable of easily and certainlywinding a heating wire on an outer peripheral portion of a core withoutcausing scattering in quality by employing automation and energy savingfor a winding step and a terminal processing step.

In accordance with the present invention, there is provided a method ofwinding a heating wire coated with an insulation resin on an outerperipheral portion of a core for forming the inner periphery of anelectrically melt-bonding joint, the method being characterized bycomprising the following steps (1) through (4):

(1) drawing out the leading end of a heating wire wound on a rewindingroller; peeling off an insulation resin at the leading end portion ofthe heating wire and connecting to a leading end portion a terminal pin;and engaging the terminal pin with an engaging piece which is rotatablealong with a core, and rotating the core so that the heating wire iswound on an outer peripheral portion of the core,

(2) continuing to rotate the core to wind the heating wire on the outerperipheral portion of the core by a predetermined number of turns;stopping the rotation of the core, and applying an electric heating irononto a wound portion of the heating wire to melt the insulation resin onthe heating wire and at the same time, melt-bonding adjacent portions ofthe wound heating wire with the molten insulation resin,

(3) starting to rotate the core to wind the heating wire on an outerperipheral portion by a predetermined number of turns; stopping therotation of the core; cutting an unwound portion of the heating wire;peeling off the insulation resin covering the heating wire near the cutportion, and fixing a terminal pin to the rear end near the cut portionof the heating wire, and

(4) engaging the terminal pin fixed to the rear end of the heating wirewith a pulling device; rotating the core while applying a tension to theheating wire so that the rear end portion of the heating wire is woundon an outer peripheral portion of the core, and applying the electricheating iron onto the heating wire near the terminal pin to melt theinsulation resin covering the heating wire and at the same time, tomelt-bond the rear end portion to the adjacent portion of the heatingwire with the molten insulation resin.

Further, in accordance with the present invention, there is provided anapparatus for winding a heating wire on a core for forming the innerperiphery of an electric melt-bonding joint which comprises a core in agenerally cylindrical shape which is capable of rotating around itsaxial center, the core being relatively moved in the axial directionwith respect to a heating wire, an engaging piece mounted on the core,which has a holding portion for holding a heating wire, and a fixingmeans to fix a terminal pin to the leading end of the heating wire,wherein the engaging piece has a holding portion for holding theterminal pin, whereby the heating wire is wound on an outer peripheralportion of the core by rotating the core.

Further, in accordance with the present invention, there is provided anapparatus for winding a heating wire on a core for forming the innerperiphery of an electrically melt-bonding joint which comprises a corein a generally cylindrical shape, an engaging piece mounted on the core,which has a holding portion for holding a heating wire, a spacing meansfor spacing the distance of the heating wire to be wound on the core, afixing means for fixing a terminal pin to the leading end of the heatingwire, means for engaging the heating wire with the spacing means, andmeans for rotating the core around its center axis and causing relativemovement of the same in its axial direction with respect to the heatingwire, whereby the heating wire is wound continuously at both sides ofthe outer periphery of the core.

In drawings:

FIG. 1 is a front view for schematically showing an embodiment of anapparatus used for the method of the present invention;

FIG. 2 is a plane view for schematically showing the apparatus shown inFIG. 1;

FIG. 3 is a schematic view in cross-section showing a step ofpeeling-off a heating wire;

FIG. 4 is a schematic view in cross-section showing a step of caulking aterminal pin;

FIG. 5 is a plane view showing a state that the terminal pin is engagedwith an engaging piece;

FIGS. 6a and 6b are a schematic view showing a state that the heatingwire is spaced;

FIGS. 7(a), (b) and (c) are schematic views showing steps that a tensileforce acting on the heating wire is released, and then, the terminal pinis connected to the rear end portion of the heating wire; and

FIG. 8 is a longitudinal cross-sectional view of an electricallymelt-bonding joint.

Preferred embodiments of the method and the apparatus according to thepresent invention will be described in detail with reference to thedrawings.

In FIGS. 1 and 2, reference numeral 1 designates a heating wire such asa nichrome wire, the outer surface of which is coated with an insulationresin such as polyethylene, polybutene or the like. The heating wire 1is wound on a rewinding roller 2 and it is drawn through a transferringdevice 3. Numeral 6 designates a core on which the heating wire 1 is tobe wound. The core 6 is rotated around its axial center and moved in itsaxial direction by means of a rotating and driving device 11 and inassociation with an automatic feeding device 12 for feeding the heatingwire from the rewinding roller 2, the rotating and driving device andthe automatic feeding device being driven by signals from a controller10.

An engaging piece 7a and a wire spacing tool 7b are respectivelydetachably mounted on an end portion of the core 6. Numeral 8 designatesan electric heating iron, numeral 9 designate a pulling device and asymbol R designates a robot, these elements being driven according tosignals from the controller 10.

The heating wire 1 wounded on the rewinding roller 2 is drawn throughthe transferring device 3 comprising guide rollers 31, a tension roller32, a nip roller 33 and so on. A cutter 34 is disposed at the feedingside of the nip roller 33 so as to cut the heating wire 1 by the aid ofa hydraulic device (not shown) or the like.

The leading end of the heating wire 1 fed through the nip roller 33 isgripped by an arm R1 of the robot R operated in association with therotating and driving device (not shown), and the heating wire 1 issuccessively transferred to operational positions for a peeling-offstep, a caulking step, a winding step and so on. A stripper 4 and acaulking device 5 are disposed near the arm R1 of the robot R.

In the peeling-off step, the insulation resin covering the leading endportion of the heating wire 1 is peeled off with the stripper 4. Asshown in FIG. 3, the stripper 4 comprises each pair of grippers 41 andcutting blades 42. The leading end portion of the heating wire 1 isgripped by the pair of grippers 41 and the free end side of the heatingwire is clamped by the cutting blades 42. Then, the cutting blades 42are moved in the direction of X in FIG. 3 so that the insulation resincovering the leading end portion of the heating wire 1 is peeled off.

In the caulking step, a terminal pin 1a is connected to the leading endportion of the heating wire 1 which has been subjected to thepeeling-off operation of the insulation resin. The terminal pin 1a issuccessively supplied by means of an aligning device such as a partsfeeder or the like (not shown). Into a connecting hole formed in theterminal pin 1a transferred through an automated system, the leading endportion of the heating wire 1 is inserted, and then, the terminal pin 1ais pressed by the caulking device 5 as shown in FIG. 4.

In the winding, the terminal pin 1a connected to the leading end portionof the heating wire 1 is fitted to the engaging piece 7a which ismounted on an end of the core 6.

As shown in FIG. 5, a notch portion or a recess 71 is formed in an uppersurface of the free end of the engaging piece 7a so as to receive theterminal pin 1a. The terminal pin 1a is engaged with the notch portion71. In this case, the spacing tool 7b is previously disengaged from theone end portion of the core 6. The core 6 is rotated around its axialcenter and at the same time, moved in the axial direction whereby theheating wire 1 is wound on an outer peripheral portion of the core.

In the winding step, it is important to wind the heating wire 1 in astate that the heating wire 1 intersects substantially in perpendicularto the axial center of the core 6. Thus, the heating wire 1 can be woundin a coil form in contact with the outer peripheral portion of the core6. In this case, it is desirable to control a pulling force to theheating wire 1 wound on the core 6 to be constant by means of thetension roller 32 or the like in the transferring device 3.

When the heating wire 1 has been wound by a predetermined number ofturns on the outer peripheral portion of the core, the rotation of thecore 6 is stopped. Then, the electric heating iron 8 is applied to thewound portion of the heating wire 1 to melt the insulation resincovering the outer periphery of the heating wire 1, whereby adjacentportions of the wound heating wire are melt-bonded with molten resin asindicated by a symbol B in FIG. 6(a). Thereafter, the winding operationto the heating wire 1 is started to an outer peripheral portion at theother end side of the core 6.

Before starting the winding of the heating wire 1 on the outerperipheral portion of the other end side of the core 6, which is stoppedto rotate, the spacing tool 7b is fitted to an end of the core, as shownin FIG. 6(a), and then, the core 6 is moved to a certain extent in thedirection of Y in FIG. 6(a) so that the heating wire 1 is engaged withthe free end portion of the spacing tool 7b. Then, the position ofstarting the winding of the heating wire 1 is determined, and then, thecore is rotated, whereby the heating wire 1 is wound by a predeterminednumber of turns on the outer peripheral portion of the other end side ofthe core 6. Then, the rotation of the core 6 is stopped. Thereafter, theelectric heating iron 8 is applied to several portions of the heatingwire 1 wound in a coil form, whereby adjacent portions of the heatingwire are joined with molten resin as shown in FIG. 6(b).

Thus, the heating wire is wound by a predetermined number of turns onthe outer peripheral portion of the other end side of the core 6 byrepeating the winding operations and the melt-bonding operations of theheating wire, and then, the rotation of the core 6 is stopped and anunwound portion of the heating wire 1 is cut with a cutter 34. The cutportion, i.e. the rear end portion of the heating wire 1 is treated topeel off the insulation resin covering the rear end portion, and aterminal pin 1a is connected to the rear end portion in the same manneras the before-mentioned operations. In this case, as shown in FIGS.7(a)-(c), the length S of the portion of the heating wire 1 where theinsulation resin is peeled off can be constant by releasing a pullingforce acting on the heating wire 1 and connecting the terminal pin 1a tothe rear end portion of the heating wire 1. Namely, in the caulking stepfor the terminal pin, the heating wire 1 gripped by the arm R1 of therobot R is cut with the cutter 34, and then, the gripping force of thearm R1 is released as shown in FIG. 7(a). Then, a tensile force actingon the heating wire 1 in the winding step is released, and at the sametime, the insulation resin covering the outer periphery of the heatingwire 1 is shrunk by a length L1 from the cut end portion. Then, a rearend portion of the heating wire 1 is gripped by the grippers 41 of thestripper 4 and cutting blades 42 are moved in the direction of X to peeloff the insulation resin at the rear end portion of the heating wire 1by a length L2. Thereafter, the terminal pin 1a is caulked and fixed tothe rear end portion. Thus, by connecting the terminal pin 1a after thetensile force acting on the heating wire 1 has been released, the lengthS of the peeled-off portion of the insulation resin can be made constantwithout causing the shrinkage of the insulation resin after theconnection of the terminal pin 1a.

Then, the terminal pin 1a connected to the rear end portion of theheating wire 1 is engaged with a pulling device 9. The core 6 is rotatedwhile a predetermined tensile force is applied to the rear end side ofthe heating wire 1 whereby the rear end portion of the heating wire 1 iswound on the outer peripheral portion of the core 6.

Finally, the electric heating iron 8 is applied to the heating wire 1 ata portion near the terminal pin 1a to thereby melt the insulation resinand join the rear end portion of the heating wire 1 to the adjoiningportion of the wire.

After the heating wire has been wound on the outer peripheral portionsof the core 6, the engaging piece 7a and the spacing tool 7b areremoved, and the core 6 is put in a metal mold. Then, molten resin suchas polyethylene, polybutene or the like is injected into a cavity formedbetween the core 6 and the metal mold whereby the electricallymelt-bonding joint A as shown in FIG. 8 can be obtained.

In the above-mentioned embodiment, the heating wire 1 is wound on anouter peripheral portion of an end side of the core 6; the spacing tool7b is used to space the heating wire on the core 6, and then, theheating wire 1 is wound on an outer peripheral portion of the other endside of the core 6. However, when the heating wire is wound continuouslywithout any space on an outer peripheral portion of the core 6, thespacing operation for the heating wire 1 is unnecessary.

Further, in the embodiment, the core is moved in the axial directionwhile the heating wire is wound on an outer peripheral portion of thecore. However, the same effect can be obtained by winding the heatingwire 1 while the heating wire 1 is moved in the axial direction of thecore 6. Further, the engaging piece 7a and the spacing tool 7b may bemounted on the rotating and driving device if the device is disposed atan end side of the core 6 on which the heating wire 1 is wound.

In accordance with a method of and an apparatus for winding a heatingwire according to the present invention, the employment of an automationsystem and energy saving in the winding step and the terminal processingstep are possible, and the heating wire can be wound easily andcertainly on an outer peripheral portion of a core.

Further, there is no danger of causing a shift or looseness of theheating wire wound on the core. Accordingly, when an electricallymelt-bonding joint is manufactured by injecting molding, a failure ofmelt-bonding due to a short circuit of the electric wire does not occur,and a product free from scattering in quality can be manufactured.

In the present invention, an electric heating iron is applied to a woundportion of the heating wire to melt insulation resin to therebymelt-bond adjacent portions of the heating wire. Accordingly, there isno shift of position of the heating wire.

Further, the heating wire can be tightly wound on the core by engaging aterminal pin fixed to an end portion of the heating wire to apply atensile force to the heating wire.

Further, after the winding of the heating wire on an outer peripheralportion of an end of the core, the rotation of the core is stopped; theheating wire is engaged with a spacing tool, and the core is started torotate. Accordingly, the heating wire is wound on an outer peripheralportion of the other end side of the core without causing a shift ofposition of the heating wire.

What is claimed is:
 1. A method of winding a heating wire coated with aninsulation resin on an outer peripheral portion of a core for formingthe inner periphery of an electrically melt-bonding joint, said methodcomprising the following steps (1) through (4):(1) drawing out theleading end of a heating wire wound on a rewinding roller; peeling offan insulation resin at the leading end portion of the heating wire andconnecting to a leading end portion of a terminal pin; and engaging theterminal pin with an engaging piece which is rotatable along with acore, and rotating the core so that the heating wire is-wound on anouter peripheral portion of the core, (2) continuing to rotate the coreto wind the heating wire on the outer peripheral portion of the core bya predetermined number of turns; stopping the rotation of the core, andapplying an electric heating iron onto a wound portion of the heatingwire to melt the insulation resin on the heating wire and at the sametime, melt-bonding adjacent portions of the wound heating wire with themolten insulation resin, (3) starting to rotate the core to wind theheating wire on an outer peripheral portion by a predetermined number ofturns; stopping the rotation of the core; cutting an unwound portion ofthe heating wire; peeling off the insulation resin covering the heatingwire near the cut portion, and fixing a terminal pin to the rear endnear the cut portion of the heating wire, and (4) engaging the terminalpin fixed to the rear end of the heating wire with a pulling device;rotating the core while applying a tension to the heating wire so thatthe rear end portion of the heating wire is wound on an outer peripheralportion of the core, and applying the electric heating iron onto theheating wire near the terminal pin to melt the insulation resin coveringthe heating wire and at the same time, to melt-bond the rear end portionto the adjacent portion of the heating wire with the molten insulationresin.